Chracterization of strain and composition in InGaN films by photoreflection and Raman scattering

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1. Strain and electric transport parameters in GaN :We have evaluated in-plane strains in GaN films from a measurement of the E2-phonon mode frequency by Raman scattering.We have also evaluated carrier concentration and mobility in n-type GaN films together with the spatial distribution by Raman scattering.Carrier concentration in p-type materials can be obtained from the intensity of inter-valence band transition of holes observed in Raman spectra.2. Spatial distribution of hexagona1- to cubic-components in GaN films :We have evaluated the ration and their spatial distribution by focusing on a characteristic feature in GaN Raman spectra.3. Composition in AIGaN and InGaN films :We have observed Raman spectra of cubic-AIGaN films for the first time for the whole range of Al composition (0-100%).We have observed various dependences of phonon frequencies on the Al content, and showed a good agreement with a theoretical model.We have also observed for the first time Raman spectra of hexagonal-InGaN films without thick GaN buffer layers in the growth process.We have observed a linear relation of the E2-phonon mode frequency on the In content of 0-7%.These results will be usable for composition characterizations.We have evaluated the bandgap energy by absorption and photoreflection measurements.The In contents were evaluated from the results and compared with Raman data on phonon frequencies.4. UV-excitation system for Raman microprobing and photo-reflection measurements :We have developed a UV-excitation system for Raman microprobing and photo-reflection measurements.We have tested the system performance by measuring Raman spectra of Si and GaN in the resonant Raman condition.